The control valve is to be serviced and maintained after normal operation. As part of the automation control system, the maintenance valve should be operated simultaneously with the automation instrument and other equipment.

      The maintenance of the control valve is similar to that of the general instrument. It can be divided into passive maintenance, preventive maintenance and predictive maintenance. Passive maintenance is a maintenance method when maintenance is performed when a valve such as a control valve fails. Due to failure of the equipment to maintain, so often cause the production process parking, or even serious equipment damage or casualties. Passive maintenance is an unwanted maintenance of the production process. Preventive maintenance is a maintenance method based on past operational experience and timekeeping. For example, the commonly used regular maintenance is preventive maintenance, it is based on the operation of different equipment to develop the appropriate maintenance schedule, the equipment has not failed to maintain. Because the failure did not occur on the maintenance, therefore, can greatly reduce the probability of failure. But this maintenance method does not currently use the actual situation of the control valve for analysis, often can also use a certain time to adjust the valve disassembly and inspection, a waste of time and resources. Predictive maintenance from the current use of the control valve data analysis, the expected state of the valve, so that the control valve to maximize the use.

Control valve routine maintenance work

The daily maintenance work of the control valve is divided into two parts: tour inspection and regular maintenance. The contents of the inspection work are as follows.

1. Talk to the process operator about the operation of the control valve.

2. Check the supply of the control valve and the relevant accessories (air supply, hydraulic oil or power supply) 3. Check the operation of the hydraulic oil system.

4. Check the control valve of the static and dynamic sealing point for leaks.

5. Check the valve connection connections and fittings for loosening or corrosion.

6. Check the control valve for abnormal sound and large vibration, check the supply situation.

7. Check the control valve is flexible, in the control signal changes whether the timely changes 8. Listen to the spool, the valve seat with abnormal vibration or noise.

9. Find the problem in a timely manner to deal with.

10. Make a record of the tour and file it.

Regular maintenance work is as follows:

1. Regularly clean the outside of the control valve.

2. Regularly adjust the valve packing and other sealing parts to adjust, if necessary, should replace the sealing parts, to keep static, dynamic sealing point of the seal.

3. Regularly add lubricant to parts to be lubricated.

4. Regularly discharge and clean the air or hydraulic filtration system.

5. Regularly check the connection point of the connection, corrosion, if necessary, should replace the connector.

Calibration of the control valve

Regulating valve predictive maintenance work has not yet carried out the unit, the valve should be checked regularly. Periodic verification work is preventive maintenance work.

Depending on the process of production, the periodic check of the control valve should have a different calibration cycle. The period of periodic calibration of each regulator can be determined in conjunction with the information provided by the manufacturer. Usually in the process of production process overhaul at the same time. Some of the control valve used in high pressure, high pressure drop or corrosive strong occasions, the test cycle to be shortened.

The main contents of the inspection valve static performance test, if necessary, can increase the corresponding test items, such as regulating valve flow characteristics of the test. Periodic verification requires testing equipment and equipment, but also need to replace the parts, therefore, usually commissioned by the manufacturer to complete.

Maintenance of the control valve

Adjustable valve repair sub-emergency maintenance, regular maintenance and predictive maintenance. Emergency maintenance is the control valve failure, can not meet the requirements of the operation of the maintenance process. Regular maintenance usually includes routine maintenance and maintenance at the same time as the process downtime. Predictive maintenance is based on the predictive maintenance of the analysis results, targeted maintenance of the valve parts. Emergency maintenance is the maintenance of the control valve after the failure, regular maintenance and predictive maintenance is the maintenance of the valve before the failure. Normally, the daily maintenance of the control valve is carried out by the instrument maintenance personnel, and the regular maintenance at the same time as the overhaul is carried out by the manufacturing technician.

      (A) of the daily inspection and maintenance of the valve, including the following:

1. Eliminate stress. Due to improper installation or combination caused by various stresses. For example, high temperature media produce thermal stress, tight installation. Solidity caused by stress imbalance. Stress imbalance in the control valve, so that the valve stem valve, the guide deformation, can not be correct with the valve seat caused by leakage, deterioration increases. Therefore, in the daily maintenance should be to eliminate the stress of the maintenance work.

2. Remove rust and dirt. Often check the control valve connection pipe with or without rust, welding slag, dirt, etc., should be promptly removed after discovery. Because these dirt will cause the valve spool valve seat and wear, affecting the normal operation of the control valve. Normally, a filter device such as a filter can be installed before the control valve and cleaned regularly.

3. Check the control valve support. The control valve supports the components of the control valve in a position that is not affected by gravity or the like. If the support will cause improper valve stem and valve seat can not be aligned, so that the increase in resistance, sealing performance. Therefore, check whether the control valve is suitable.

4. Remove the air supply, hydraulic oil and other energy supply of dirt. Air source, hydraulic source is the energy source of the valve operation. Instrument with compressed air, hydraulic oil contained in the impurities will plug the orifice and pipe, causing failure. Therefore, regular inspection of air supply, hydraulic oil, the regular discharge of the filter device is very important.

5. Inspection of gear transmission. Hand wheel institutions, electric actuators and hydraulic actuators of the gear transmission should be regularly checked, add lubricant to prevent the occurrence of bite card phenomenon. Should check the brake and limit device is flexible and easy to use.

6. Packing letter check. Should check the filler wear and compression force, regular replacement stuffing box to ensure that the filler can play a sealed at the same time, to reduce the friction of the shadow port. Lubricants should not be added to oil-free stuffing stuffing.

7. Check for safe operation. The safety valve, such as the tightening of the sealing cap, the operation of the safety barrier, the supply of power supply, etc., shall be carried out in such a way that the control valve and the relevant accessories used in the explosive hazardous areas shall ensure safe operation of the regulating valve and related accessories.

8. Transport and custody. When the control valve is in the transportation and storage, the application of special bracket fixed to prevent loosening; installed in the control valve on the accessories, such as the valve positioner, hand wheel mechanism should be strong, should be connected with the control valve connected to the feedback lever and other components by external force Damage; the connection interface application of plastic film envelope to prevent foreign objects intrusion; control valve connection can be used to match the flange and blind plate seal, can also be used viscous paper seal to prevent foreign objects intrusion. Transport should be installed in a solid wooden box, and take weather, rain and dust and other adverse environmental conditions of transport. The environmental conditions for transport and storage shall meet the requirements of the product specification.

      (B) control valve and accessories The main contents of routine maintenance are as follows:

1. Pneumatic actuator diaphragm replacement. The diaphragm of the pneumatic film actuator is stretched and contracted during operation, so that fatigue is easily damaged. Replacement should be used with the specifications of the rubber diaphragm, should be tight when the diaphragm force evenly to prevent leakage and pressure diaphragm.

2. Grinding Spool and valve seat between the operation after a certain period of time caused by leakage, the cylinder between the piston and the cylinder will also cause internal leakage, then should be grinding. Can be handmade grinding, mechanical grinding, coating and inlay and other methods, grinding with the diamond particle size should be appropriate, grinding force should be uniform and appropriate. After grinding, should be polished, and meet the required finish and precision requirements to meet the valve core and the seat of the alignment requirements, after the assembly required to be sealed test.

3. Replacement of stuffing box. Packing material should be replaced with the same type of stuffing box, the replacement should be careful to fill out the filler, the correct removal of filler, to prevent damage to the stem. The installation of the new packing letter should be in accordance with the requirements of the instructions, the incision should be dislocation, to prevent the stem thread on the filler scratches, packing pressure should be uniform and appropriate to prevent stress and increase friction.

4. Replacement of transmission parts. If the parts in the control valve and the accessory are partially worn, parts can be replaced, repaired, and so on. In the replacement and repair should ensure that the transmission flexibility, transmission gap as small as possible.

5. Pneumatic amplifier cleaning. Due to the use of compressed air within the air caused by the pneumatic amplifier throttle plug when the throttle should be cleaned, you can use the appropriate wire to clear and clean. When installed, the amplifier diaphragm should be evenly stressed to prevent clogging or leakage. The gain of the amplifier can be adjusted by adjusting the pressing force of the ball to prevent resonance.